Electrostatics is concerned with the electrical fields and scalar potentials of stationary electrical charges and charge distributions. Use this for questions about electromagnetic situations in which currents and magnetic fields are absent, otherwise use [tag:electromagnetism] and/or ...

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How can we verify the direction of electric displacement is radial?

I have two questions about electric displacement $D$. The following is a problem in Griffiths. A long straight wire, carrying uniform line charge $\lambda$, is surrounded by rubber ...
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1answer
48 views

Why is there no electric potential energy when it is directly above an electric dipole?

If you have two opposite charges of equal magnitude, why is the potential energy of another random particle that is directly above or below the middle distance between the two charges have 0 electric ...
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4answers
56 views

Same equation, different meanings

I went into a physics classroom today and saw this equation written on the board: $$ E = \frac \sigma \epsilon $$ At first I thought it referred to the electric field $ E $ between 2 parallel plates ...
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1answer
14 views

Why are pressure/potential differences across a barrier measured from inside to outside?

I don't know if I'm asking clearly, but I'm a Medical Student who is trying to intuitively understand pressure differences and electrochemical gradient (across a semipermeable membrane) differences. ...
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4answers
121 views

Charge inside a charged spherical shell

If I were to put a negative charge inside a negatively charged spherical shell, will it move to the center? Electric field inside the shell due to the shell is zero (Gauss's Law), would that mean ...
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0answers
29 views

Series expansion of potential due to a dipole displaced from the origin

I learn that we can expand the electric potential in an infinite series of $\rho$ and $\cos(n \phi)$ when solving the Laplace equation in polar coordinates. The problem I want to consider is the ...
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0answers
50 views

Where to place a charge to establish net force of 0? [closed]

A charge, Q2 = -15.00x10^-6 C, is 10.00 cm to the right of charge Q1 = 18.00x10^-6 C. Where can a third charge be placed, along the line connecting Q1 and Q2, such that it experiences no net force ...
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2answers
60 views

How do two metal balls of radius $r$ kept at a large distance form a capacitor? [closed]

So this is something really new to me. I have learnt of plate capacitors, cylindrical capacitors, single spherical capacitors, etc. but that to, of finite distance between them. Also please explain if ...
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119 views

distribution of electric charges

In electricity courses, in the lesson on static fields, at some point all teachers say "let's consider a large rectangular metal plate where the density of charges is uniform", and then they proceed ...
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2answers
117 views

metal die charged, where do the charges go?

I'm puzzled by this question: I have a metal die (a regular cube, completely filled with homogeneous iron for instance); I charge it with some µCoulombs. Where do the charges go? Can the faces of the ...
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1answer
130 views

Atoms, Gravity and Electrostatic Charge [closed]

How close do 2 atoms of any type the have can be together before gravity with an electrostatic charge that repulses?
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42 views

Electric Field at a point some distance above a uniformly charged cylinder

In this problem I am trying to solve, I am trying to find the electric field at a point directly above a uniformly charged cylinder. The cylinder is oriented so that the two round face are parallel ...
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0answers
41 views

Why is the susceptibility $\chi(t)$ real?

So my question is quite simple I suppose, and perhaps trivial. It is known that the frequency domain susceptbility $\chi(\omega)$ is complex, and that the two parts can be related with the ...
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1answer
34 views

Relation between dipole moment and polarisaton

In the Landau's book "Electrodynamics of Continuous Media" he derives the relation between the polarisation $\vec P$ and the dipole moment $\vec p$. Starting with the definition of the dipole moment: ...
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1answer
47 views

How and why do electric fields occur when we put a voltage difference between two point?

When we put a voltage differences between two points on a certain sample, I would like to know how and why the electric field occurs. In addition, I would like to know in what shape does the electric ...
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1answer
39 views

Understanding of dipole moment and its vector property

I have a trouble understanding the electric dipole moment. The electric dipole moment formula is $${\bf p}= \int {\bf r}' \rho({\bf r}')d\tau '$$ I'm interested in the coordinate, the origin of which ...
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1answer
55 views

Earnshaw's Theorem and Plum Pudding

I'm trying to understand what Thompson's motivation for his Plum-pudding model was. He chose the nucleus to be a sphere of uniform charge because it was mathematically nice, and chose the charge to be ...
3
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2answers
130 views

Charging by induction [closed]

When we charge an conductor by induction and grounding, we first bring a negative charge to the conductor. As a result the mobile electrons of the conductor get repelled and stay far from the negative ...
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2answers
51 views

electric field inside a conducting body [closed]

From Gauss' Law, we know that the electric field inside a solid conducting sphere varies linearly with the distance from the centre. But we also know that electric field inside a conductor is zero. ...
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1answer
47 views

What does the tangent line to a general curved electric field line denote?

Just want to see the tangent line which indicates the line of electric force. What is tangent line?
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2answers
54 views

Question about using Gauss' Law with a surface at infinity

While doing homework, I came across a situation where I tried to make this argument: For a finite distribution of charges, I know that the electric field drops off to zero at infinity. So therefore, ...
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1answer
35 views

Electrostatics problems

In image method we use image charge to calculate field and potential at any point and we replace induced charge by image charge.But why dont we directly calculate field and potential for induced ...
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1answer
55 views

Electric field's area [closed]

How much area an electric field surrounds? since we're just able to draw the electric lines of force we sometimes think that the field is though 3d but surrounds a finite area. But is it measurable or ...
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1answer
69 views

Does Gauss's law not hold when there are charges outside of the Gaussian surface?

For example, if I have a gaussian surface and a negative charge somewhere outside that gaussian surface, there's going to be a non-zero electric flux. However, According to gauss's law, electric ...
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1answer
31 views

Can polarization occur if both charges are neutral?

If I keep neutral conductive pieces of some metal close to a neutral conductive sheet, what will happen? Will any of them get polarized or nothing will happen. My guess is nothing will happen as for ...
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0answers
33 views

What does the density of points (tail point of the vectors) represent in the geometrical representation of a vector field? [closed]

While trying to understand the divergence of a vector through the geometrical representation of the vector field, I found that pictures can be misleading. Even a vectors field which looks to be ...
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0answers
31 views

Poisson's equation inside a sphere with linear charge distribution

Consider the Poisson equation \begin{equation*} \nabla^2\Phi = -4\pi \rho \end{equation*} inside a sphere of radius $b$. The charge density $\rho(x)$ corresponds to an evenly distributed charge $Q$ ...
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39 views

Charge on Earth [closed]

We know that the Earth is neutral. But what will happen if the Earth becomes negatively charged or positively charged somehow?
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1answer
44 views

Physics Static Electricity [duplicate]

If a person has plastic soles, and are playing on Artificial grass and then the person touches metal goal post, the person will get a static shock.. Why?
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0answers
19 views

Electric field on the surface of conductor? [duplicate]

I know that field inside the conductor is zero but what about the field on the surface of conductor? And is the surface of conductor equipotential?And please explain why?
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1answer
45 views

What will be the effect on coulomb force if any conductor is placed between the electric charges?

I know that if any insulator or dielectric is placed between the electric charges then coulomb force decreases by factor known as dielectric constant.So, what will the effect when any conductor is ...
3
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3answers
101 views

What does the Dirac delta function physically do while deriving Gauss Law form Coulomb's law?

While doing this derivation, the the source coordinates are mentioned as "$s$" and the coordinate of the point at which field is to be calculated is mentioned as "$r$". Kindly follow this Wikipedia ...
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1answer
52 views

Why aren't +/- test leads connected to battery terminals attracted to each other?

Similar to static electricity, why wouldn't the negative charges accumulate on the wire connected to the negative terminal of a battery be attracted to the positive wire (lead) when their ends are ...
3
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2answers
105 views

Electric Field “at” the surface of a conductor

It has been pointed out to me that the Electric field exactly on the surface of the conductor is conventionally taken to be $E=\frac{\sigma}{2\epsilon_0}$; does this come from taking the midpoint of ...
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0answers
110 views

Capacitance of two non parallel plates with two dielectric materials

There is one answered question about the two non parallel plate capacitance here. However, it only has one dielectric material. I am looking for a formulae of the same configuration, but with 2 ...
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1answer
55 views

Will charges attract or repel?

If the universe consist of only two particles namely electron and proton, and if they are separated away by huge distance, they will still attract each other. Can we prove it without using Coulomb's ...
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1answer
25 views

Force from a large conducting plate [closed]

How can I find the distance to a test-charge, hoovering below a conducting plate? Newtons laws applies. $$ $$ According to this information, I conclude that the force is equal zero. It is not ...
3
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2answers
73 views

Gauss Law Not Working Inside Cavity

When I apply gauss law inside a cavity within uniformly charged solid sphere then I get that $$\oint E.dA =Q _{enclosed}/{\epsilon_{0}}$$ Which should imply that $E=0$ since enclosed charge is 0. ...
3
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1answer
30 views

Static electricity: Why did this happen?

The other day I experienced a discharge of static electricity. It was unusually strong, so strong that it almost hurt. I would like to hear your answers to how such a strong static charge could have ...
3
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1answer
66 views

Solved Gauss' Law for $\vec{E}$ without boundary conditions?

Why can I solve for the electric field of a point charge Q at the origin without boundary conditions? $\nabla\cdot\vec{E}=\rho/\varepsilon_0 = \delta(\vec{r})/\varepsilon_0$ is a 1st order ...
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1answer
37 views

What is the difference between charged body and conductors?

In charged bodies,charges can be uniformly distributed all over it's volume, but in conductors charges always lies on it's surface. Please tell me the difference between charged bodies and ...
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0answers
147 views

electric field due to a square loop via algebraic instead of symmetry [closed]

Below is problem 2.4 adapted from Introduction to Electrodynamics by David Griffiths. Find the electric field a distance z above the center of a square loop(of side a ) carrying uniform line charge ...
2
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0answers
144 views

Electrostatics question about three identical styrofoam balls suspended from a fixed point, asking to solve for charge? [closed]

Three identical small Styrofoam balls ($m = 2.06\ \text{g}$) are suspended from a fixed point by three nonconducting threads, each with a length of $46.6\ \text{cm}$ and with negligible mass. At ...
3
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0answers
45 views

Lightning sprites

Lightning usually occurs due to an electrostatic discharge between an electrically-charged cloud and the Earth's surface, or between clouds. There are also sprites, electrical discharges that occur ...
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1answer
49 views

Source charge at the origin of a 13 polygon surrounded by 13 equal charge at each corners

Suppose there are 13 equal charges at each corners of an $n=13$ regular polygon. The test charge $Q$ lies at the origin of the $n=13$ regular polygon. In the case of an $n=12$ regular polygon, the ...
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1answer
49 views

Why is it true that Laplace's equation does not hold within the sphere in this case?

Find the average potential over a spherical surface of radius $R$ due to a point charge $q$ located inside. (In this case Laplace's equation does not hold within the sphere) This is a question ...
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90 views

Divergence theorem and discontinuous vector fields in electrostatics

Wikipedia defines Gauss Divergence Theorem for a continuously differentiable vector field; but in many idealized physical situations, we use it for non-differentiable fields. For example, the electric ...
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0answers
58 views

Gauss's law giving incorrect answer

Let's consider two concentric spherical shells, one of radius $R$ and one of radius $R - \Delta R$. The outer shell is negatively charged and the inner shell positively, but both the shells have net ...
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1answer
147 views

Distribution of surface charges in an electric circuit

I'm reading Sherwood and Chabay's brilliant textbook Matter and Interactions, in particular the section that deals with how the surface charges in an electric circuit distribute themselves to generate ...
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0answers
15 views

Would a previously poled piezoelectric material experience a force aligning it with an external electric field?

I'm wondering if it would possible to crush a poled PZT object, disperse the powder into a thermoplastic (with a melt temperature below the Curie temperature of PZT) and align the 'crystal shards' ...